(1) Transition metal ions can change their oxidation states, hence they are effective as catalysts.
(2) They are good catalysts because of lower valencies due to which they sometimes form an unstable intermediary and hence a new path with lower activation energy
(3) Transition metal catalysts are always heterogeneous catalysts where the catalyst and reactants are in different phases.
(4) In some cases transition metals provide a suitable surface for adsorption which weakens the bond between reactant molecules making them good catalysts
$\begin{array}{1 1} All \;are\;correct \\(1), (2) \;and\; (4)\; are\; correct \\ (2), (3) \;and\; (4)\; are\; correct \\ (1), (2) \;and\; (3) \;are\; correct \end{array}$
